U.S. solar and biofuel companies are struggling to find new top executives after a string of departures over the past year, demonstrating a lack of faith among executives that the sector can recover from a supply glut that has hammered share prices.

Almost all the top U.S.-listed solar companies, including First Solar Inc, SunPower Corp, Canadian Solar Inc and JA Solar Holdings Co, have seen either their CEO or CFO leave over the past year.

The turnover has coincided with a rapid decline in solar companies’ pricing power as subsidy cuts in Europe hit demand and surging production in China adds to supplies.

With frequent changes and very little succession planning, investors are getting increasingly frustrated.

The WilderHill Clean Energy index, which includes the shares of companies such as First Solar, Suntech Power Holdings Co Ltd and Trina Solar Ltd, has more than halved in the past year.

“As the fundamentals have become more difficult, the sector has certainly lost some appeal as management tasks have certainly become less rewarding,” said Sustainable Asset Management’s Thiemo Lang, a senior portfolio manager who manages a fund that has $900 million in cleantech assets under management.

Flush with funds from venture capitalists and strong backing from governments the industry, set up to develop a new generation of cleaner technology, gave executives their moments under the sun for more than a decade.

But throughout, there was more churn than that seen in more mature sectors, where an executive is likely to spend their professional life in one or two companies.

Sanjeev Kumar, the CFO at solar inverter maker Enphase Energy Inc who is leaving the company later this year, has served in the role at five different companies, mostly cleantech, over the last 12 years.

Enphase’s shares fell by a quarter immediately after Kumar’s departure was announced earlier this month. Efforts to contact Kumar through Enphase were unsuccessful.

First Solar lost about a quarter of its value on Oct. 25 after the solar panel maker ousted CEO Rob Gillette.

“Frequent executive searches take up valuable time of board members and entail the use of costly consultants,” said Raymond James analyst Pavel Molchanov.

“Having to adapt to varying management styles can be taxing for lower-level staff, potentially affecting morale.”

Biofuel companies are also suffering as incentives fall and the economy stays weak.

At biofuels and biochemicals maker Codexis Inc, which counts Royal Dutch Shell Plc as a partner, executive churn has reached another level.

Codexis said in January CFO Robert Lawson had quit to join a private software company. CEO Alan Shaw resigned the next month, and was replaced by John Nicols in June. A few days later in June, interim finance head Brian Dowd quit.

“Uncertainty hurts the company,” said Wes Bolsen, chief marketing officer at Codexis. “People ask like who’s leading the company? What’s the vision for the company going forward?”

Codexis, which has lost half of its market value this year, is still looking for a CFO.